The present invention relates to a remote control apparatus for a transmission which performs remote control operation of a transmission by utilizing auxiliary power.
Large-sized buses have been developed in recent years, and engines are mounted in rear body portions in such buses. Along with this change in mounting position of the engine, a transmission or gear box is also mounted in the rear body portion. In a conventional transmission control mechanism, when a driver operates a change lever, an operation force is transmitted to the transmission mounted in the rear body portion through a link mechanism.
Operation of such a conventional transmission system requires a large force. In order to decrease the operation force, auxiliary power utilizing compressed air has been recently used to shift the transmission position. The auxiliary power is controlled upon operation of the change lever. In this manner, light gear transmission like in normal passenger cars can be performed even in heavy-duty vehicles such as buses. When the auxiliary power is used for gear transmission, the gear shift can be smoothly performed, and a large operation force can be easily produced. Therefore, the gear shift time can be shortened.
FIGS. 1A to 1E are respectively diagrams for explaining the operation of the transmission in the related art. Referring to FIGS. 1A to 1E, reference numerals 1R and 1I denote reverse and first-speed gear shift jaws; 1II and 1III, second- and third-speed gear shift jaws; 1IV and 1V, fourth- and fifth-speed gear shift jaws; and 2, a striker of a gear shift unit for performing shift and selection (to be described later) in synchronism with movement of a change lever. Among these shift jaws, the shift jaws 1R and 1I are formed integrally with a gear shift fork 4, as shown in FIG. 2. The shift jaws 1R and 1I and the gear shift fork 4 are fixed on a shift rail 5. When the striker 2 is inserted in a groove 3 and is axially moved along the shift rail 5, the shift jaws 1R and 1I engaged with the striker 2 are axially moved along the shift rail 5. This movement is referred to as a shift hereinafter, and the moving direction is referred to as a shift direction. When the shift jaws 1R and 1I are shifted, the shift fork 4 integrally formed with the shift jaws 1R and 1I is shifted along the shift direction. A gear (not shown) engaged with the shift fork 4 is shifted along the shift direction, so that the transmission is set in the reverse or first-speed gear position. In other words, when the striker 2 is shifted to the left in FIG. 2, the reverse position state shown in FIG. 1A is set. However, when the striker 2 is shifted to the right in FIG. 2, the first-speed gear position state is obtained, as shown in FIG. 1B.
The structure of other shift jaws, i.e., the shift jaws 1II and 1III or the shift jaws 1IV and 1V is the same as the shift jaws 1R and 1I formed to define the groove 3 there between. When the striker 2 is inserted in the groove 3 defined by the shift jaws 1II and 1III or the shift jaws 1IV and 1V and is shifted along the shift direction, the corresponding shift jaws are also shifted accordingly.
As shown in FIG. 2, the shift jaws are aligned along the shift rail 5. When the striker 2 is inserted in the groove 3 and is shifted along the shift direction, the striker 2 is brought into contact with one of the two shift jaws. However, when the striker 2 is moved along a direction away from the groove 3 and perpendicular to the axial direction of the shift rail 5, the striker 2 can be disengaged from the groove 3. Movement of the striker 2 along a direction perpendicular to the axial direction of the shift rail 5 is defined as selection and its direction is defined as a "select direction".
Three pairs of shift jaws are arranged adjacent to each other, as shown in FIGS. 1A to 1E. When the shift state shown in FIG. 1A or 1B is given, the striker 2 cannot be removed from the groove 3 defined by the shift jaws 1R and 1I due to the presence of the jaw 1II or 1III. However, when the change lever is set in the neutral position, the striker 2 is located at the position shown in FIG. 1C. The striker 2 can be inserted in the groove 3 of the adjacent pair of shift jaws 1II and 1III. In the state of FIG. 1C, selection can be performed along the right select direction. When the striker 2 is inserted in the groove 3 defined by other shift jaws and is shifted, the gear shift corresponding to the groove 3 is performed.
The gear shift is performed in synchronism with movement of the change lever upon shifting of the striker 2 along a given shift direction. When the striker 2 returns from a shift position to the neutral position, it is moved along a given select direction and is shifted along any shift direction, thereby completing the gear change. Since the striker 2 is shifted and selected by the auxiliary power of compressed air, the force required for movement of the change lever is minimized.
For example, when the gear shift is performed from the first-speed gear position to the second-speed gear position, the striker 2 is shifted from the state of FIG. 1B to the state of FIG. 1C. The striker 2 performs selection, as shown in FIG. 1D. Thereafter, the second-speed gear position is set. The above operation sequence is very short since the auxiliary power is utilized. The shift jaws 1R and 1I are formed integrally with the shift fork 4 having a larger mass than those and the reverse and first-speed gears (not shown) engaged with the shift fork 4, as shown in FIG. 2. When the shift jaws 1R and 1I, the shift fork 4 and the reverse and first-speed gears are shifted as a mass from the state of FIG. 1B to the state of FIG. 1C at a high speed, a larger inertia force is generated. When the mass reaches the state of FIG. 1C, the striker 2 is immediately moved in the select position. In this case, since the inertia force of the mass including the shift jaws 1R and 1I is sufficiently left, the shift jaws 1R and 1I cannot be stopped in the state of FIG. 1D and overshoot. As a result, the state of FIG. 1E is given before the striker 2 is shifted, and the reverse state is obtained.
When the reverse state is obtained, the striker 2 abuts against the shift jaw 1I and can no longer be inserted in the groove 3 defined by the shift jaws 1R and 1I. The transmission is locked in the reverse state. Since the shift rail 5 has a double gear engagement prevention unit (not shown), second- or third-speed gear shift cannot be performed.
Since the reverse and first-speed gears do not have a synchromesh arrangement, the transmission tends to be locked in the reverse state. However, the same phenomenon occurs even in other speed gears.
In order to prevent this phenomenon, an interlock plate 6 is proposed, as shown in FIG. 3. The interlock plate 6 has a groove 6a and projections 6b and 6c formed at two sides of the groove 6a. When the striker 2 is inserted in the groove 6a and is moved in the select direction, the interlock plate 6 is also moved along the same select direction. The projection 6b or 6c is fitted in the groove 3 of the selected shift jaw, thereby preventing overshooting of the shift jaw.
In order to absorb the large inertia force, the interlock plate in the groove 6a and is moved in the select direction, the interlock plate 6 is also moved along the same select direction. The projection 6b or 6c is fitted in the groove 3 of the selected shift jaw, thereby preventing overshooting of the shift jaw.
In order to absorb the large inertia force, the interlock plate 6 must have enough rigidity and becomes high cost, and mounting and adjustment thereof is time-consuming, thus increasing the cost of the transmission.